PF4 and leukemia: NK-92 cells migration directed toward factors present in a pre-cleared leukemia cell (Kasumi) supernatant placed in the lower chamber of Transwell plates was significantly reduced (p < 0.001) by AML exosomes (Fig. 4a) These AML exosomes carried high levels of CXCL4, CXCL7, and CCL5 (RANTES) relative to the reference HD exosomes in antibody microarrays (Fig. 4b).